St.Louis' Magic House has an online presidential quiz with 2 questions each day for kids. This is a good test for adults as well, with questions about presidential elections and other presidential trivia going back to Washington. If you ever worried about being stopped on the street and asked American history questions by Jay Leno or someone from another comedy channel, this would be a good page to shore up your knowledge.
The daily test began last Wednesday so at this moment there are only 5 quizes. It goes to day 20.